Terahertz Functional Devices Based on Multilayer Flexible Metasurface

The scientific and technological interest in the terahertz (THz) metasurfaces, composed of artificial sub-wavelength unit-cell structures, has been gradually increasing because unusual electromagnetic properties cannot be achieved by natural materials. Developing metasurface-based THz components including filters, couplers, and modulators, with high performance are essential in tailoring the desired electromagnetic properties and synthesizing complex waveforms. Here, filtering functional devices are designed in thin film materials with high flexibility and stability, which makes the device durable and compact. We report a novel THz filter design strategy that combines a multilayer sandwich with a periodic array microstructure to perform both lowpass and wide bandwidth bandpass filters with a steeper skirt and huge out-of-band rejection. Cascading the designed lowpass filter and bandpass filter can improve the high-frequency harmonic suppression by superimposing their respective filtering performance under the premise that the passband index has little influence, which is one of the bright spots of our design.